Language:
Standard Modular System came before System 360 and its Solid Logic Technology The Standard Modular System (SMS) was a innovative system of standard transistorized circuit boards and mounting racks developed by IBM in the late 1950's.. SMS was superseded by Solid Logic Technology (SLT) Introduced with the System/360 Computer in 1964, however they remained in use with legacy systems through the 1970s.
SMS cards were constructed of individual components mounted on single sided paper-epoxy printed circuit boards. An SMS card would typically have 3 to 6 germanium transistors and 15 or so resistors, plus about half a dozen capacitors and diodes. A board might contain a flip-flop or a few simple gates.Some card types could be customized via a "program cap" (a small double rail metal jumper bar with 15 connections) that could be cut to change the circuit configuration. This feature was intended to reduce the number of different card types.
When SMS was originally developed in 1955, IBM anticipated a set of a couple hundred standard card types would be all that would be needed. Unfortunately that proved far too optimistic as the number of different SMS card types soon grew to well over 2500. Part of the reason for the growth was that multiple digital logic families were implemented (ECL, RTL, DTL, etc.).
next